Karyotypic evolution in breast carcinomas with i(1)(q10) and der(1;16)(q10;p10) as the primary chromosome abnormality.

The pattern of clonal karyotypic evolution in breast carcinomas carrying an i(1q) or a der(1;16)(q10;p10) as the primary chromosome abnormality was assessed in a series of 42 tumors, including 8 described here for the first time, with either or both (3 tumors) of them defining cytogenetic features. Evidence of clonal evolution was seen in somewhat more than half of all cases in both subgroups. The secondarily acquired aberrations appeared to be nonrandom in distribution. This was especially so for structural rearrangements of 11q leading to loss of material from this arm, which were clearly more common in both subgroups than in karyotypically abnormal breast carcinomas in general. Other deviations from random were less certain but seemed to include the frequent occurrence of +20 in tumors with i(1q) and +7 in tumors with der(1;16)(q10;p10). That differences were observed between i(1q) carcinomas and der(1;16)(q10;p10) carcinomas with regard to their patterns of clonal evolution hints that the pathogenetic effect of the primary change in these two situations may be more than the mere gain of an extra copy of 1q.     

Quantitative multigene FISH on breast carcinomas identifies der(1;16)(q10;p10) as an early event in luminal A tumors

In situ detection of genomic alterations in cancer provides information at the single cell level, making it possible to investigate genomic changes in cells in a tissue context. Such topological information is important when studying intratumor heterogeneity as well as alterations related to different steps in tumor progression. We developed a quantitative multigene fluorescence in situ hybridization (QM FISH) method to detect multiple genomic regions in single cells in complex tissues. As a “proof of principle” we applied the method to breast cancer samples to identify partners in whole arm (WA) translocations. WA gain of chromosome arm 1q and loss of chromosome arm 16q are among the most frequent genomic events in breast cancer. By designing five specific FISH probes based on breakpoint information from comparative genomic hybridization array (aCGH) profiles, we visualized chromosomal translocations in clinical samples at the single cell level. By analyzing aCGH data from 295 patients with breast carcinoma with known molecular subtype, we found concurrent WA gain of 1q and loss of 16q to be more frequent in luminal A tumors compared to other molecular subtypes. QM FISH applied to a subset of samples (n = 26) identified a derivative chromosome der(1;16)(q10;p10), a result of a centromere‐close translocation between chromosome arms 1q and 16p. In addition, we observed that the distribution of cells with the translocation varied from sample to sample, some had a homogenous cell population while others displayed intratumor heterogeneity with cell‐to‐cell variation. Finally, for one tumor with both preinvasive and invasive components, the fraction of cells with translocation was lower and more heterogeneous in the preinvasive tumor cells compared to the cells in the invasive component. © 2014 The Authors Genes, Chromosomes & Cancer Published by Wiley Periodicals, Inc.     

Follicular thyroid carcinoma: Chromosome analysis of 19 cases

Short-term cultures of 19 follicular thyroid carcinomas were examined cytogenetically. Clonal chromosomal changes were detected in 12 tumors. Two follicular carcinomas had only numerical alterations: one with a hyperdiploid karyotype with trisomies/polysomies of chromosomes 7 and 12, similar to the karyotypes previously identified in a sub-group of benign thyroid lesions, and the other with monosomy 20. In the remaining ten cases several structural chromosome anomalies were found. Loss of the short arm of chromosome 3 was observed in one tumor. In two widely invasive and metastasizing follicular carcinomas there was a t(7;8)(p15;q24) as the sole abnormality in one case and a der(8)t(7;8)(p15;q24) together with other cytogenetic alterations in the other case. This finding suggests that t(7;8)(p15;q24) may be related to an aggressive behavior of follicular thyroid carcinomas. Genes Chromosomes Cancer 21:250–255, 1998. © 1998 Wiley-Liss, Inc.     

Allele loss in Wilms tumors of chromosome arms 11q, 16q,and 22q correlates with clinicopathological parameters

An extended analysis for loss of heterozygosity (LOH) on eight chromosomes was conducted in a series of 82 Wilms tumors. Observed rates of allele loss were: 9.5% (1p), 5% (4q), 6% (6p), 3% (7p), 9.8% (11q), 28% (11p15), 13.4% (16q), 8.8% (18p), and 13.8% (22q). Known regions of frequent allele loss on chromosome arms 1p, 11p15, and 16q were analyzed with a series of markers, but their size could not be narrowed down to smaller intervals, making any positional cloning effort difficult. In contrast to most previous studies, several tumors exhibited allele loss for multiple chromosomes, suggesting an important role for genome instability in a subset of tumors. Comparison with clinical data revealed a possible prognostic significance, especially for LOH on chromosome arms 11q and 22q with high frequencies of anaplastic tumors, tumor recurrence, and fatal outcome. Similarly, LOH 16q was associated with anaplastic and recurrent tumors. These markers may be helpful in the future for selecting high-risk tumors for modified therapeutic regimens. Genes Chromosomes Cancer 22:287–294, 1998. © 1998 Wiley-Liss, Inc.     

Noninvolvement of a constitutional heritable fragile site at 10q24.2 in rearranged chromosomes from rectal carcinoma cells

A fragile site in chromosome band 10q24.2 was found in the lymphocytes of a patient ascertained for rectal carcinoma. The karyotype of 110 R-banded tumor cells was performed, showing two stemline formulas: 46,XXY,-1,-18,+20,der(6),t(1;6)(q21.1;q22.3),i(17q) and 46,XY,-1,-18,+8,+20,der(6),t(1;6),del(2)(p1600p22),i(17q). These findings are in agreement with our previous studies, which reported that the rearrangement of chromosome #17 and the loss of chromosome #18 are recurrent anomalies in colorectal carcinomas. In addition to these rearrangements, other anomalies were occasionally observed in tumor cells, but no breakages nor rearrangements involving band 10q24.2. The relationships between fragile sites and cancer breakpoints are discussed.     

Loss of chromosome 16q in lobular carcinoma in situ

Lobular carcinoma in situ (LCIS) and infiltrating lobular carcinoma may represent different forms of the same disease based on their frequent clinical association and similar histologic features. Patients with LCIS are at increased risk of multicentric and bilateral disease. Thus, LCIS may represent both a precursor to infiltrating lobular carcinoma and a marker of risk for breast cancer. To identify genomic alterations in LCIS, comparative genomic hybridization was performed on 17 cases without concurrent invasive carcinoma. Loss involving chromosome 16q was present in 88% of cases and was the sole detected alteration in 29%. Gain involving 1q was second in frequency, occurring in 41% of tumors, and in all cases was associated with loss of 16q. Other recurrent changes were loss involving 17p (18%), 8p (12%), and 12q24 (12%). E-cadherin immunohistochemistry was performed on all LCIS cases to evaluate the correlation of loss involving 16q22, the site of the E-cadherin gene, and altered protein expression. Most cases with 16q22 loss showed altered E-cadherin expression (12 of 13). These results in LCIS are similar to changes reported in infiltrating lobular cancer, confirming a genetic relationship between them. HUM PATHOL 32:292-296.     

Two-color FISH characterization of i(1q) and der(1;16) in human breast cancer cells

Two-color fluorescent in situ hybridizations using probes for alphoid (α) and classical satellite (CS) DNAs from chromosomes 1 and 16 were performed to characterize i(1q), der(1;16), and complex rearrangements observed in breast cancer cells from fresh tumors and established cell lines. Six of seven i(1q) occurred after breakage in the α1 containing region and one of seven was dicentric, with breakage in 1p11.2. The five der(1;16)(q10;p10) studied appeared to result from a variety of breakpoints involving α1, α16, CS1, and CS16 DNAs. All had conserved α16 DNA, suggesting a segregation of the der(1;16) leading to a loss of 16q and a gain of 1q in most cases. One complex rearrangement of chromosome 1 also appeared to involve chromosome 16, suggesting that a der(1;16) occurred first, followed by another rearrangement. Both the apparent preferential involvement of constitutive heterochromatin harboring α and CS DNAs and the variety of breakpoints spanning along heterochromatin suggest that the important consequence of the rearrangement is not the breakage per se but the resulting imbalance. © 1993 Wiley-Liss, Inc.     

Cytogenetic analysis of pancreatic carcinomas: Intratumor heterogeneity and nonrandom pattern of chromosome aberrations

Twenty-nine nonendocrine pancreatic carcinomas (20 primary tumors and nine metastases) were studied by chromosome banding after short-term culture. Acquired clonal aberrations were found in 25 tumors and a detailed analysis of these revealed extensive cytogenetic intratumor heterogeneity. Apart from six carcinomas with one clone only, 19 tumors displayed from two to 58 clones, bringing the total number of clones to 230. Karyotypically related clones, signifying evolutionary variation, were found in 16 tumors, whereas unrelated clones were present in nine, the latter finding probably reflecting a distinct pathogenetic mechanism. The cytogenetic profile of pancreatic carcinoma was characterized by multiple numerical and structural changes. In total, more than 500 abnormal chromosomes, including rings, markers, homogeneously stained regions, and double minutes, altogether displaying 608 breakpoints, were detected. This complexity and heterogeneity notwithstanding, a nonrandom karyotypic pattern can be discerned in pancreatic cancer. Chromosomes 1, 3, 6, 7, 8, 11, 12, 17, and 19 and bands 1q12, 1q21, 3q11, 6p21, 6q21, 7q11, 7q22, 7q32, 11q13, 13cen, 14cen, 17q11, 17q21, and 19q13 were most frequently involved in structural rearrangements. A total of 19 recurrent unbalanced structural changes were identified, 11 of which were not reported previously: del(1)(q11), del(3)(p11), i(3)(q10), del(4)(q25), del(11)(p13), dup(11)(q13q23), i(12)(p10), der(13;15)(q10;q10), del(18)(q12), del(18)(q21), and i(19)(q10). The main karyotypic imbalances were entire-copy losses of chromosomes 18, Y, and 21, gains of chromosomes 7, 2, and 20, partial or whole-arm losses of 1p, 3p, 6q, 8p, 9p, 15q, 17p, 18q, 19p, and 20p, and partial or whole-arm gains of 1q, 3q, 5p, 6p, 7q, 8q, 11q, 12p, 17q, 19q, and 20q. In general, the karyotypic pattern of pancreatic carcinoma fits the multistep carcinogenesis concept. The observed cytogenetic heterogeneity appears to reflect a multitude of interchangeable but oncogenetically equivalent events, and the nonrandomness of the chromosomal alterations underscores the preferential pathways involved in tumor initiation and progression. Genes Chromosomes Cancer 23:81–99, 1998. © 1998 Wiley-Liss, Inc.     

Familial reciprocal translocation, t(2;10)(p24;q26), resulting in duplication 2p and deletion 10q

We describe a familial reciprocal translocation between the distal part of the short arm of chromosome 2 and the long arm of chromosome 10. Five individuals in two generations had multiple congenital anomalies. Their karyotypes were 46, XX or XY,−10, + der(10), t(2;10)(p24;q26). Seven persons were balanced translocation carriers whose karyotypes were 46, XX or XY, t(2;10)(p24;q26). Common manifestations included mental retardation, strabismus, narrow high-arched palate, wide alveolar ridges, other facial abnormalities, genital abnormalities and mutism. The phenotype of the unbalanced individuals is compared to that of previously published cases of the syndrome of partial duplication 2p and to reported patients with partial deletion of 10q.     

Chromosomal changes during progression of transitional cell carcinoma of the bladder and delineation of the amplified interval on chromosome arm 8q

The cascade of genetic alterations leading to malignant transformation has been described for adenocarcinoma of the colon but is not established for other common tumor entities. In the present study, different stages of transitional cell carcinoma (TCC) of the bladder are analyzed by comparative genomic hybridization. A dynamic pattern of the chromosomal changes during tumor progression is described. Deletion of chromosome arm 9q is the earliest genetic alteration in pTa tumors. In stage pT1 carcinomas, losses of 9q, 9p, and 11p and gain of 1q and 8q are the most common. In addition to the changes specific for earlier stages, gain of 5p and 20q becomes prominent in carcinomas stage ≥pT2. Association analysis reveals a remarkable cooccurrence of 9p deletion with gain of 5p and 20q in ≥pT2 tumors. In order to determine more precisely the size of the amplified segment and the degree of amplification on chromosome arm 8q in stage pT1 tumors, this region was analyzed by semiquantitative PCR using polymorphic microsatellite markers. These studies revealed an up to 13-fold amplification. The common region of amplification could be narrowed down to 8q22.3 and between GAAT1A4 and D8S1834 (about 7 cM). Genes Chromosomes Cancer 23:167–174, 1998. © 1998 Wiley-Liss, Inc.     

A constitutional bws-related t(11;16) chromosome translocation occurring in the same region of chromosome 16 implicated in wilms' tumors

Beckwith-Wiedemann syndrome (BWS) is a congenital overgrowth disorder with a varying spectrum of clinical manifestations including macroglossia, omphalocele, hemihypertrophy, and a predisposition to a subset of embryonal tumors, most frequently Wilms' tumor (WT). A variety of cytogenetic, genetic linkage, and molecular mapping data implicate a gene or genes on chromosome band 11p15.5 in BWS and its related tumors. However, some families with BWS do not show linkage to 11p15, and other alterations have been found in Wilms' tumors as well. One such alteration is loss of heterozygosity (LOH) for chromosome arm 16q. Here we have analyzed a balanced t(11;16)(p15;q13) chromosomal translocation associated with the BWS phenotype and mapped the breakpoint positions for both chromosomes 11 and 16 by using somatic cell hybrids and polymorphic markers. The chromosome 11 breakpoint was found to lie distal to the D11S12 locus, but proximal to TH on 11p15.5, a region shown previously to contain other BWS-related chromosomal events. The chromosome 16 breakpoint was distal to D16S290 in 16q13, but proximal to loci D16S265, D16S267, and D16S164 in band 16q21. This area encompasses the region of LOH occurring through mitotic recombination in sporadic WT. This raises interesting possibilities for the genetic and epigenetic involvement of both chromosomal regions (11p15 and 16q13) in the pathogenesis of BWS and Wilms' tumor.     

Comparative genomic hybridization detects frequent overrepresentation of chromosomal material from 3q26, 8q24, and 20q13 in human ovarian carcinomas

We used comparative genomic hybridization (CGH) to identify recurrent chromosomal imbalances in tumor DNA from 25 malignant ovarian carcinomas and two ovarian tumors of low malignant potential (LMP). Many of the carcinoma specimens displayed numerous imbalances. The most common sites of copy number increases, in order of frequency, were 8q24.1, 20q13.2-qter, 3q26.3-qter, 1q32, 20p, 9p21-pter, and 12p. DNA amplification was identified in 12 carcinomas (48%). The most frequent sites of amplification were 8q24.1-24.2, 3q26.3, and 20q13.2-qter. Other recurrent sites of amplification included 7q36, 17q25, and 19q13.1-13.2. The most frequent sites of copy number decreases were 5q21, 9q, 17p, 17q12-21, 4q26-31, 16q, and 22q. Underrepresentation of 17p was observed in six of 16 stage III/IV tumors, but in none of seven stage I/II tumors, suggesting that this change may be a late event associated with the transition of ovarian carcinomas to a more metastatic disease. Overrepresentation of 3q26.3-qter, 5p14-pter, 8q24.1, 9p21-pter, 20p, and 20q13.2-qter and underrepresentation of 4q26-31 and 17q12-21 also tended to be more common in advanced-stage tumors. All ten grade 3 tumors had copy number increases involving 8q24.1, compared to only three of nine grade 2 tumors. Overrepresentation of 3q26.3-qter and 20q13.2-qter was also observed at a higher frequency in high-grade tumors. One of the two LMP tumors displayed chromosomal alterations, which consisted of overrepresentation of 5p and 9p only. Taken collectively, these findings and data from other CGH studies of ovarian cancers define a set of small chromosome segments that are consistently over- or underrepresented and, thus, highlight sites of putative oncogenes and tumor suppressor genes that contribute to the pathogenesis of these highly malignant neoplasms. Genes Chromosomes Cancer 20:320–328, 1997. © 1997 Wiley-Liss, Inc.     

Demonstration of the translocation der(16)t(1;16)(q12;q11.2) in interphase nuclei of ewing tumors

The der(16)t(1;16) has been detected cytogenetically in a number of malignancies including Ewing tumors (ETs). To enable fast and reliable analysis of der(16) chromosomes, we established an interphase cytogenetic approach. By using two DNA probes hybridizing to the heterochromatic portions on the long arms of chromosomes 1 and 16, this technique allows the detection of this chromosomal aberration in nonproliferating cells. Formation of the der(16) leads to partial excess of 1 q material and partial loss of the long arm of chromosome 16. Double-target fluorescence in situ hybridization (FISH) experiments were performed on cytospin slides of 13 ETs, near-triploid tumor cells and normal cells to assess whether the FISH technique used permits the discrimination of nuclei harboring this aberration from nuclei without a der(16) chromosome. In five ETs, we found evidence for the presence of one or two der(16)t(1;16) chromosomes both by FISH and by conventional cytogenetics. Tumor cells displayed two signals for intact chromosomes 1, one or two additional fused signals for the der(16) chromosomes, and one signal for the intact chromosome 16. In one case without fused signals, the presence of a der(16) was demonstrated by hybridizing a painting probe for chromosome 16 simultaneously with the paracentromeric probe for chromosome 1. Our results suggest that double-target FISH on interphase nuclei offers an ideal tool for analyzing tumors prospectively and retrospectively to assess the biological role and the possible prognostic impact of the der(16) in ETs and in other solid tumors. Genes Chromosom Cancer 17:141–150 (1996) © 1996 Wiley-Liss, Inc.     

t(10;16)(q22;p13) and MORF-CREBBP fusion is a recurrent event in acute myeloid leukemia

Recently, it was shown that t(10;16)(q22;p13) fuses the MORF and CREBBP genes in a case of childhood acute myeloid leukemia (AML) M5a, with a complex karyotype containing other rearrangements. Here, we report a new case with the MORF-CREBBP fusion in an 84-year-old patient diagnosed with AML M5b, in which the t(10;16)(q22;p13) was the only cytogenetic aberration. This supports that this is a recurrent pathogenic translocation in AML.     

Interphase cytogenetics for 1p19q and t(1;19)(q10;p10) may distinguish prognostically relevant subgroups in extraventricular neurocytoma

Co-deletion of chromosome arms 1p and 19q, characteristic of oligodendroglial tumors, was recently found to be mediated by t(1;19)(q10;p10). To evaluate the prevalence of 1p19q co-deletion and t(1;19) in extraventricular neurocytomas (EVN), we studied tumors from 23 patients, including 13 females and 10 males (median age at diagnosis 34 years, range 2–76 years). Fluorescence in situ hybridization (FISH) studies were performed with probes targeting 1p36/1q25 and 19q13/19p13 to assess for 1p19q co-deletion, as well as chromosome 1 α-satellite and 19p12 to detect t(1;19)(q10;p10). FISH was successful in 21 (91%) cases and demonstrated 1p19q co-deletion in five cases (24%) or isolated 1p loss in two cases (10%). Evidence for t(1;19) was found in four (of five) cases with 1p19q co-deletion. Three tumors with 1p19q loss and t(1;19) demonstrated atypical histologic features, compared with one (of 17) tumors without 1p19q co-deletion ( P  = 0.01, Fisher exact test). In addition, tumors with t(1;19) showed increased mitotic activity compared with tumors without t(1;19) ( P  = 0.045; Wilcoxon rank sum test). The four patients with t(1;19) developed tumor recurrence (n = 3), or expired (n = 2) 3.5 to 5.5 years after first resection. These results suggest that 1p19q loss and t(1;19) occur in a subset of EVN, and may be associated with aggressive histology in these tumors.     

Pediatric acute myeloid leukemia with t(7;21)(p22;q22)

The t(7;21)(p22;q22) resulting in RUNX1‐USP42 fusion, is a rare but recurrent cytogenetic abnormality associated with acute myeloid leukemia (AML) and myelodysplastic syndromes. The prognostic significance of this translocation has not been well established due to the limited number of patients. Herein, we report three pediatric AML patients with t(7;21)(p22;q22). All three patients presented with pancytopenia or leukopenia at diagnosis, accompanied by abnormal immunophenotypic expression of CD7 and CD56 on leukemic blasts. One patient had t(7;21)(p22;q22) as the sole abnormality, whereas the other two patients had additional numerical and structural aberrations including loss of 5q material. Fluorescence in situ hybridization analysis on interphase cells or sequential examination of metaphases showed the RUNX1 rearrangement and confirmed translocation 7;21. Genomic SNP microarray analysis, performed on DNA extracted from the bone marrow from the patient with isolated t(7;21)(p22;q22), showed a 32.2 Mb copy neutral loss of heterozygosity (cnLOH) within the short arm of chromosome 11. After 2‐4 cycles of chemotherapy, all three patients underwent allogeneic hematopoietic stem cell transplantation (HSCT). One patient died due to complications related to viral reactivation and graft‐versus‐host disease. The other two patients achieved complete remission after HSCT. Our data displayed the accompanying cytogenetic abnormalities including del(5q) and cnLOH of 11p, the frequent pathological features shared with other reported cases, and clinical outcome in pediatric AML patients with t(7;21)(p22;q22). The heterogeneity in AML harboring similar cytogenetic alterations may be attributed to additional uncovered genetic lesions.     

Allelic imbalance study of 16q in human primary breast carcinomas using microsatellite markers

The high incidence of allelic imbalance on the long arm of chromosome 16 in breast cancer suggests its involvement in the development and progression of the tumor. Several loss of heterozygosity (LOH) studies have led to the assignment of commonly deleted regions on 16q where tumor suppressor genes may be located. The most recurrent LOH regions have been 16q22.1 and 16q22.4-qter. The aim of this study was to gain further insight into the occurrence of one or multiple “smallest regions of overlap” on 16q in a new series of breast carcinomas. Hence, a detailed allelic imbalance map was constructed for 46 sporadic breast carcinomas, using 11 polymorphic microsatellite markers located on chromosome 16. Allelic imbalance of one or more markers on 16q was shown by 30 of the 46 tumors (65%). Among these 30 carcinomas, LOH on the long arm of chromosome 16 was detected at all informative loci in 19 (41%); 13 of them showed allelic imbalance on the long but not on the short arm, with the occurrence of variable “breakpoints” in the pericentromeric region. The partial allelic imbalance in 11 tumors involved either the 16q22.1-qter LOH region or interstitial LOH regions. A commonly deleted region was found between D16S421 and D16S289 on 16q22.1 in 29 of the 30 tumors. The present data argue in favor of an important involvement of a tumor suppressor gene mapping to 16q22.1 in the genesis or progression of breast cancer.     

Derivative (1;18)(q10;q10): a recurrent and novel unbalanced translocation involving 1q in myeloid disorders.

We report two cases of hematological malignancies, comprising a case of myelodysplastic syndrome (MDS) that rapidly evolved into acute myeloid leukemia, and a case of myeloproliferative disorder (MPD), in which der(1;18)(q10;q10) was found as the sole acquired karyotypic abnormality. This observation indicates that the unbalanced translocation is a recurrent aberration in myeloid disorders. To the best of our knowledge, centromeric fusion between long arms of chromosomes 1 and 18, leading to a normal chromosome 18 substituted with a der(1;18) chromosome, is novel and has not been described in cancer. Mechanistically, either trisomy 1q or monosomy 18p that results from the translocation may potentially contribute to leukemogenesis. Finally, chromosomes with large constitutive heterochromatin bands such as chromosome 1 may be at risk of centromeric instability and be predisposed to centromeric fusion with other chromosomes.     

Rearrangement between the MYH11 gene at 16p13 and D12S158 at 12p13 in a case of acute myeloid leukemia M1 (AML-M1)

A case of acute myeloid leukemia (AML) M1 with bone marrow eosinophilia was characterized by cytogenetics and fluorescence in situ hybridization (FISH). A complex karyotype including a der(12)t(12;17)(p12-13;q11) and a der(16)t(16;20)(p13;p11) was found at diagnosis. FISH studies with probes for chromosome 16 and for the short arm of chromosome 12 showed even more complex rearrangements. Analysis with a panel of probes for 12p showed that D12S158 spanned the breakpoint on the der(12). Unexpectedly, FISH signals were found on the der(12) and on the der(16) at band p13, the site of juxtaposition between the short arm of chromosome 16 and chromosome 20. Moreover, both YAC 854E2, containing the MYH11 gene, and cosmid ZIT133, encompassing the MYH11 breakpoint in inv(16) and t(16;16) of AML-M4 with eosinophilia, demonstrated fluorescent signals on the normal 16, on the der(16), and on the der(12). These data clearly support a reciprocal exchange between D12S158 at 12p13.3 and the MYH11 gene at 16p13. In addition, experiments with two PAC clones for the CBFB gene at 16q22 excluded the presence of a masked inv(16). An interstitial deletion, independent from the translocation and flanked by VWF and KRAS2, was also detected on the der(12). Genes Chromosomes Cancer 23:10–15, 1998. © 1998 Wiley-Liss, Inc.